Insights from NMR Spectroscopy into the Conformational Properties of Man-9 and Its Recognition by Two HIV Binding Proteins

Chembiochem. 2017 Apr 18;18(8):764-771. doi: 10.1002/cbic.201600665. Epub 2017 Mar 22.

Abstract

Man9 GlcNAc2 (Man-9) present at the surface of HIV makes up the binding sites of several HIV-neutralizing agents and the mammalian lectin DC-SIGN, which is involved in cellular immunity and trans-infections. We describe the conformational properties of Man-9 in its free state and when bound by the HIV entry-inhibitor protein microvirin (MVN), and define the minimum epitopes of both MVN and DC-SIGN by using NMR spectroscopy. To facilitate the implementation of 3D 13 C-edited spectra to deconvolute spectral overlap and to determine the solution structure of Man-9, we developed a robust expression system for the production of 13 C,15 N-labeled glycans in mammalian cells. The studies reveal that Man-9 interacts with HIV-binding proteins through distinct epitopes and adopts diverse conformations in the bound state. In combination with molecular dynamics simulations we observed receptor-bound conformations to be sampled by Man-9 in the free state, thus suggesting a conformational selection mechanism for diverse recognition.

Keywords: NMR spectroscopy; carbohydrate recognition; glycan conformation; isotopic labeling; molecular dynamics.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • A549 Cells
  • Bacterial Proteins / chemistry*
  • Carbohydrate Conformation
  • Carbon Radioisotopes
  • Cell Adhesion Molecules / chemistry*
  • HIV Envelope Protein gp120 / chemistry
  • HIV Envelope Protein gp120 / metabolism
  • HIV-1 / metabolism
  • Humans
  • Lectins, C-Type / chemistry*
  • Magnetic Resonance Spectroscopy*
  • Mannans / biosynthesis
  • Mannans / chemistry*
  • Mannose-Binding Lectin / chemistry*
  • Microcystis
  • Molecular Dynamics Simulation
  • Nitrogen Radioisotopes
  • Receptors, Cell Surface / chemistry*

Substances

  • Bacterial Proteins
  • Carbon Radioisotopes
  • Cell Adhesion Molecules
  • DC-specific ICAM-3 grabbing nonintegrin
  • HIV Envelope Protein gp120
  • Lectins, C-Type
  • Mannans
  • Mannose-Binding Lectin
  • Nitrogen Radioisotopes
  • Receptors, Cell Surface
  • mannosyl(9)-N-acetylglucosamine2
  • microvirin protein, Microcystis aeruginosa